The present invention relates to a method of controlling the revolution speed and the torque of a synchronous motor provided with a field generating mechanism including a rotor of magnetic anisotropy, and a control apparatus for controlling the same synchronous motor.
In a conventional synchronous motor incorporated in a machine tool for instance, an armature (stator) and a rotor are provided, and further field poles are formed by arranging permanent magnets on the rotor or by winding coils around the rotor so as to be excited by a dc current. The number of poles is usually from 2 to 8.
Similarly, in a conventional generator, an armature and a stator are provided in the same way as with the case of the synchronous motor, and the field poles are formed by winding coils as electromagnets.
In the conventional synchronous motor or the generator, however, since the permanent magnet or magnets are provided on the rotor or the coil or coils are wound around the rotor, there exist various problems in that the structure is complicated and thereby weakened and further the rotor is deformed or damaged at high speed thereof. In addition, when incorporated in a machine tool in order to drive a main spindle thereof, the conventional motor cannot satisfy the various requirements such as constant output characteristics in a wide speed range, a smooth revolution without torque pulsation, a stable shape free from any thermal deformation due to heat generated by the rotor, etc.